Versatile transmitter and receiver for position measurement

ABSTRACT

Field-deployable spatial positioning or measurement systems are provided for improved versatility, reliability and performance. The spatial positioning or measurement systems use rotating laser fans or beams for positioning and measuring and include a system integrated field-deployable length standard that uses a reelable tape with positional indents. The systems further include the use of labyrinth seals at interface volumes between rotating laser heads and transmitter assemblies to prevent ingress of contaminants and allow for elimination of the use of rotary seals. Further, new dynamic leveling techniques are provided to plumb positional laser transmitter systems. Still further, strobe beam configurations are provided for improved near/far performance and a vertical mode sensing scheme that allows switching to measuring tall structures when needed.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of U.S. patent applicationSer. No. 10/302,081, filed Nov. 22, 2002. This application also claimspriority to U.S, patent application Ser. No. 09/803,664 filed Mar. 09,2001, now abandoned, and U.S. Provisional Application Serial No.60/188,367, filed Mar. 10, 2000.

[0002] This invention relates to field-deployable spatial positioning ormeasurement systems. Specifically, the present invention providesspatial positioning or measurement systems that use novel systemhardware, calibration methods and transmission/detection modes toprovide increased ease-of-use, better reliability, increased systemlongevity, easier calibration methods, wider usable range and improvedversatility. As such, the spatial positioning or measurement systemsaccording to the various embodiments of the present invention arecapable of providing high resolution, reproducible and accurate spatialor position measurements in two or three dimensions thus allowingenhanced accuracy and utility for use in surveying and construction andmanufacturing layout. The present invention may also be used forapplications including spatial data generation for design of vehicularsystems or vector and tensor mapping such as accumulating data relatingto temperature, wind shear, electric fields, radiation flux, etc.

[0003] Present uses for field-deployable spatial positioning systemsinclude construction layout such as setting reference points or settingcontrol lines, asymptotes and similar geometric boundaries or guidelines; laying out parallel or perpendicular lines; measuring lineardistances between points; navigating to specific points entered by auser; and establishing working planes. Such uses may include generationof level or sloped plane references for earthwork and site preparation;generation of vertical (plumb) plane references for tilt-up wallplacement; and XY (2-D) or XYZ (3-D) coordinate measurement forpositioning concrete forms, footers, and anchor bolts.

[0004] Additional uses for field-deployable spatial positioning systemsinclude machine control or robotic applications, and transfer ofmeasurement or spatial positioning data to and from CAD systems ordatabases.

[0005] Prior art field-deployable spatial positioning and measurementsystems include those described in U.S. Pat. Nos. 4,874,238; 5,100,229;5,110,202; 5,579,102; 5,461,473; 5,294,970; and 5,247,487, all of whichare hereby incorporated by reference in their entirety. Spatialpositioning systems described in these patent references usuallycomprise a single “laser transmitter” and a single “laser receiver”. Thetransmitter is placed at a fixed location and serves as a measurementreference or beacon for the receiver. The handheld receiver is carriedby the user and displays in real-time the location of the receiverrelative to the transmitter. Because of mathematical constraints, such asingle-transmitter system is only capable of measuring the horizontal(azimuth) and vertical (elevation) angular location of the receiver;that is, no direct measurement of the range from the transmitter toreceiver is possible. A more advanced system consists of two or moretransmitters and a single receiver. The transmitters are again placed atfixed locations, and serve the same purpose as before. The receivercalculates its azimuth and elevation location relative to eachtransmitter. If the transmitters are at known locations, the receivercan then calculate its position in 3-D space using known methods andalgorithms, e.g., see U.S. Pat. No. 5,100,229 as cited above. In eitherthe single or multi-transmitter systems, multiple receivers may be usedsimultaneously with the same transmitter(s). This is possible since thetransmitters only serve as a reference or beacon, in the same way thatGPS satellites serve as a reference for many users. Calculations todetermine the location of a given receiver take place in that receiver,not the transmitter(s).

[0006] As will be described more fully below, the primary components ofa transmitter can include the following: a rotary laser head containingtwo laser assemblies; a spindle assembly including a motor and encoderfor spinning the rotary laser head; an optical strobe assembly thatfunctions as an azimuth reference to establish a “zero” angle for theazimuth angle; a gimbal assembly including level sensors and motors forleveling the rotary laser head; and control electronics needed toperform various functions including sensing, balancing, monitoring,position determination, user interfacing and data output. The rotarylaser head contains two laser assemblies that produce two fannedinfrared laser beams perpendicular to the spin axis of the head asdescribed in the above-reference U.S. patents. The radial axes of thefan beams can be chosen to be separated by approximately 90 degrees (orother angle) around the head. The fan beams are also rotatedapproximately 30 degrees in opposite directions about their respectiveradial axes.

[0007] The rotating laser head is attached to the top end of a shaftthrough the spindle assembly. The lower end of the shaft is attached toa motor and rotary encoder. The motor spins the shaft, and thus the headat a known, constant speed. The rotary encoder is used to sense therotation speed of the shaft and provides feedback to the motor drivecircuit in the control electronics.

[0008] As is described in the above-reference U.S. patents, an opticalstrobe assembly can be used to synchronize, or set a rotation datum for,the azimuthal angle swept by the fanned beams. This can be implementedas a ring of outward-facing IREDs (infrared emitting diodes) locatedjust below the rotating laser head. The strobe is stationary, andmounted to the outside of the spindle assembly. Using feedback from therotary encoder on the shaft, the control electronics cause the strobe toemit a very short flash of infrared light once per revolution of thehead, or any other set interval. This flash is detected by the mobilereceiver and used as a zero azimuth angle reference.

[0009] The gimbal assembly is attached to the outside of the spindleassembly, and connects it to the outer housing of the transmitter. Thepurpose of the gimbal assembly is to allow a tilt (in two axes) in aknown manner of the rotary head spin axis relative to the outer housing.In most applications it is desirable, for reasons to be explained below,to plumb the spin axis of the head with respect to gravity (or to someother desired axis). If this is done, the radial axes of the fan lasers,which are perpendicular to the spin axis, will sweep through a planethat is level with respect to gravity. In order to plumb the spin axis;the control electronics reads the output of the level sensors, which areattached to the outside of the spindle assembly, and drives the motorsof the gimbal assembly until the sensor outputs indicate that the spinaxis is plumb. Well known electrolytic vials can be used as monitors inassisting this feedback function.

[0010] Control electronics govern the overall operation of the lasertransmitter. As mentioned above, the electronics control the rotationspeed of the head by using the rotary encoder output as feedback. Theelectronics further trigger the optical strobe once per revolution ofthe head and plumbs the spin axis by moving the gimbal assembly based onfeedback from the level sensors.

[0011] The primary components of the receiver generally include thefollowing: a detector such as a (photodiode) assembly for sensing theoptical strobe and fan lasers from the transmitter(s); timingelectronics for measuring the time between received pulses; a processor,such as a microprocessor, for calculating the location of the receiver;and a user interface such as a display and keypad. The detector orphotodiode assembly produces an electrical output in response to theoptical strobe signal from the transmitter(s). The detector orphotodiode assembly also produces an output pulse whenever crossed byone of the rotating fan beams from a transmitter. For example, when thedetector is in the vicinity of a single transmitter, the output for onecomplete rotation of the transmitter head can include times T1, T2, andTrev measured by timing electronics, where T1 is the time between a(received) strobe light pulse and a first fanned laser beam; T2 is thetime between a strobe light pulse and a second fanned laser beam; andTrev is the time between strobe pulses.

[0012] The microprocessor calculates the angular location of thereceiver relative to the transmitter by using the output of the timingelectronics. Since the strobe is omnidirectional, the absolute time atwhich the strobe pulse is received is independent of the position of thereceiver. The two fan beams projected from the transmitter are tipped 30degrees in opposite directions about their radial axes, which areseparated by 90 degrees about the rotating laser head. Therefore theelevation (vertical) angle of the receiver relative to the transmitterwill be a function of the time between the received laser pulses, andthe azimuth (horizontal) angle will be a function of the average timefrom the strobe to the two laser pulses as given, for example, in U.S.Pat. No. 5,110,202 cited above. If the speed of rotation of thetransmitter head is very steady, the angular position of the receivermay be calculated as:

azimuth angle=360*(T1+T2)/(2* Trev)  Eqn. 1

[0013] $\begin{matrix}{{{elevation}\quad {angle}} = {\frac{{360*{\left( {{T1} + {T2}} \right)/{Trev}}} - 90}{2}*{\cot (30)}}} & {{Eqn}.\quad 2}\end{matrix}$

[0014] The result of these calculations is output in various formats onthe display, depending on the particular application. The keypad allowsthe user to control the operating mode.

[0015] One aspect of such a spatial positioning system is the use of alength standard to set a scale for the spatial positioning systembecause the above scheme often measures the azimuthal and elevationangles only, depending on the number of transmitters and the systemfunctions selected. With a single detector and transmitter, for example,the distance between the two is unknown. One method of estimating thedistance is to perform a “stadia measurement”, which is a commontechnique in surveying. This measurement can be performed with twodetectors (such as photodiodes) mounted; to a straight rod a knowndistance apart (e.g., 2 meters). Both detectors would be connected tothe same receiver, which would then simultaneously calculate the angularposition of each detector relative to the transmitter. Since thedistance between the detectors is known, the receiver can make arelatively crude estimate of the distance from the rod to thetransmitter. This method is suitable if highly accurate measurements arenot required, but suffers from parallax type error, especially over longranges in the field of measurement.

[0016] If more accuracy is required, a multi-transmitter system may beused. This system is capable of calculating accurate 2-dimensional or3-dimensional positions of a single-detector receiver. The basicmeasurement is the same as in the single-transmitter system; that is,the receiver calculates its angular location relative to eachtransmitter. Mathematically, the location of the receiver relative to agiven transmitter is somewhere along a vector that starts at thetransmitter and passes through the receiver. If the transmitters are atknown locations, then solving for the intersection of the vectorsextending from each transmitter to the receiver will give coordinates ofthe receiver. More precisely, the coordinates found are at the center ofthe detector or photodiode.

[0017] However, for systems using only one transmitter or for systemsusing multiple transmitters where increased accuracy and resolution isdesired, a scaling reference is needed. One usually introduces a linearscale or distance reference into a known setup procedure for thispurpose. Since the basic measurements made are all angular, and thetransmitters and setup points are at arbitrary locations, inherent scalein the system can be obtained by several means. For example, a scale baror tape measure can be used. When, for example, the user measures apoint at each end of an object that is exactly one meter long and thereceiver is told that the distance between these points is one meter;then the receiver can adjust the scale of the relative coordinate systemto give measurements in meaningful units such as meters, inches, feet,etc. The measurement of this scale reference object must be done veryaccurately, since the operating distance multiplies any error in thescale reference. That is, if a 1 mm error is made in measuring a 1 mscale reference, then the absolute position error at a distance of 50 mis 50 mm. Therefore it is desirable to use long scale references, suchas a 10 meter scale reference.

[0018] A second aspect for such a spatial positioning system,particularly if it is to be field-deployable, is that contaminants arekept out of certain critical areas containing vital components like thespindle shaft and shaft bearings.

[0019] A third aspect for the spatial positioning system is thedesirability of a leveled transmitter to enhance the accuracy of themeasurements that are made. With the automatic leveling described above,there is still a need for frequent and continued calibration of suchleveling in the transmitter units. This calibration is vital foraccuracy and usability. From the outset, initial manufacturingtolerances must be set before new transmitters are sold. Transmittersthat are dropped, or subject to excessive mechanical vibration shouldpreferably be re-calibrated, and six month periodic calibration areusually recommended and expected. Calibrations are also often requiredafter removal and replacement of mechanical components such as therotating laser head or spindle assembly. Finally, preparation andcertification of a used transmitter for sale would require closecalibration of the auto-leveling system.

[0020] A fourth aspect of such a spatial positioning system is that theoutput light or energy from the strobes used to synchronize theazimuthal fan sweep should preferably cover the field of measurement andbe of sufficient strength to be detected without ambiguity and with ahigh enough signal to noise ratio in the control or sensing electronics.

[0021] A fifth aspect of such a spatial positioning system is thatfiduciary volume over which the transmitter-receiver combination canfunction should preferably cover the desired field of measurement, suchas when doing spatial positioning of tall or high structures.

[0022] In the prior art, there are problems associated with each ofthese requirements.

[0023] The first aspect of setting a scale is made difficult by havingto measure a ruler, tape, or other reference in the field. Accuracy cansuffer, as noted above, due to measurement errors. Reproducibility cansuffer from using different length standards, or using the samestandard, but with slightly different deployment, such as when a tapemeasure is not pulled to the same tightness from measurement tomeasurement.

[0024] The second aspect for keeping contaminants out of selected areasor away from critical components in the transmitter has not beenadequately addressed. Typically one uses rotary seals, which introducefriction associated with spinning the rotating laser head. This addedfriction can reduce battery life in the transmitter. Rotary seals alsointroduce vibrations and shaft wobble, that, while subtle, can affectaccuracy and reproducibility for coordinate measurements, especiallyover a large field of measurement. Degradation of such rotary seals canreduce system longevity and can send bits of elastomer or other debrisinto the protected areas, and can release trapped dirt as well.

[0025] The third aspect for a calibration of the automatic leveling in atransmitter is quite onerous, and requires use of known elaborateprocedures using measurement stands, sensors, and the like. Such presentcalibrations are very time consuming, and require the laser output to bepainstakingly and manually compared to benchmarks and references in asetup stand. This can take hours per unit, and drives up costs. Carefulwork is required, and setup errors are not well tolerated, resulting inoverall calibration errors.

[0026] The fourth aspect for strobe or synchronization distributionsuffers from severe tradeoffs in usable range and signal strength. Lightemitting devices that have narrow solid-angle output distributions thatare suitable for long distance “reaching” of the strobe beam to farlocations in the field of measurement are inadequate for measurementsclose to the transmitter, especially down low or up high. Conversely,light emitting devices that have wide solid-angle output distributionsthat are suitable for good wide coverage of measurement very close tothe transmitter are inadequate for measurements far from thetransmitter, because their output intensity drops rapidly as a functionof distance from the strobe.

[0027] The fifth aspect of keeping a large usable range for verticaltypes of measurements cannot be addressed with present fanned beamtransmitters because the divergence or extent of the fan beams used arenot sufficient to cover the entire field of measurement, and can sufferfrom “fringe” effects where the crispness or quality of the beam fansdegrades at large divergence angles. When the usable range ofmeasurement over the field of measurement suffers because the workingspace or fiduciary volume subtended by the capabilities of spatialpositioning system operation is limited, such as when working in thevertically extended environments, the system cannot be used. Suchconditions come up often, such as when tilting pre-fabricated walls to avertical position. Conventional spatial positioning systems cannot spanthe necessary vertical fiduciary volume over which accurate measurementsmust be made, unless a transmitter dedicated to laser sweeps in avertical plane is used.

[0028] It is therefore an object of this invention to provide afield-deployable length standard that is built into the spatialpositioning system receiver with capability to reproduce faithfully theforce loading of the length standard for greater accuracy. It is also anobject to provide protection against contaminant entry without the useof rotary seals or other conventional means used in the spatialpositioning system field that have not met with great success withoutthe drawbacks mentioned. It is a further object of this invention toprovide a method of calibration the leveling of a transmitter which iseasy to implement, accurate, and tolerant of setup errors. It is yet afurther object of this invention to provide a scheme for synchronizationstrobe beam distribution which maximizes usable range for both near andfar measurements with respect to the transmitter. It is another objectof this invention to provide a way to use the same transmitter forvertical types of measurements, while allowing use of the same controlelectronics and calibration procedures as cited in the third requirementabove. Other objects will become apparent upon reading of thespecification.

SUMMARY OF THE INVENTION

[0029] One general embodiment disclosed includes a transmitter andspatial positioning receiver for a spatial positioning system. Thetransmitter comprises a stationary portion and a rotating laser head inproximity to the stationary portion. The rotating laser head comprises afirst light emitting device operatively configured to emit a divergentrotating light fan onto a field of measurement. The transmitter alsocomprises a synchronization strobe operatively configured to provide asynchronization strobe beam. The spatial positioning receiver alsoincludes a detector operatively configured to detect the divergentrotating light fan and also the synchronization strobe beam when thespatial positioning receiver is operating in the field of measurement.Additionally, the system also includes a processor programmablyconfigured to determine at least one spatial coordinate of the detectorin the spatial positioning receiver based on a time of receipt of atleast one of the divergent rotating light fan and the synchronizationstrobe beam from the transmitter.

[0030] The transmitter and spatial positioning receiver also comprise afield-deployable length standard for use with the spatial positioningreceiver for spatial position-marking, setting, calibrating orreferencing in the spatial positioning system. This field-deployablelength standard comprises a reelable tape comprising at least onemarkable position. The reelable tape and the markable position are eachpositioned and oriented with respect to the spatial positioning receiversuch that when the spatial positioning receiver is moved from a firstlocation to a second location and upon unreeling the reelable tape andusing the markable position, a detector in the spatial positioningreceiver is a known distance from the first location of the detector inthe spatial positioning receiver prior to unreeling the reelable tape.

[0031] Additionally, the transmitter is so constructed so that thestationary portion and the rotating laser head are each individuallypositioned, shaped, and oriented such that there is defined an interfacevolume therebetween. The transmitter then further comprises a labyrinthseal, so sized, positioned and oriented so as to restrict the motion ofcontaminants through the interface volume between the rotating laserhead and the stationary portion of the transmitter.

[0032] Additionally, there is found a strobe set to provide a spatialpositioning transmitter synchronization strobe beam to improve energydistribution and operating range when communicating with the spatialpositioning receiver operating in the field of measurement. The strobeset further comprises a first strobe having an output distribution of afirst value for half power beam angular width, oriented to provideoutput onto the field of measurement. A second strobe is provided havingan output distribution of a second value for half power beam widthhigher than the first value for half power beam angular width, orientedto provide output onto the field of measurement. The first and secondstrobes are further positioned and oriented such that the operatingrange of the spatial positioning receiver is increased with respect tothe first and second strobes both having either the first value or thesecond value for half power beam angular width. The transmitter can alsocomprise a sensor to sense when the transmitter is oriented so as tosweep the divergent rotating light fan in a substantially verticalplane, with the sensor communicating the sense to the processor for avertical coordinate determination.

[0033] Other embodiments of the inventions described herein will bedescribed below, and individually, some embodiments have only some ofthe elements thus far cited. For example, we disclose a field-deployablelength standard for use with a spatial positioning receiver for spatialposition-marking, setting, calibrating or referencing in a spatialpositioning system, the field-deployable length standard comprising areelable tape comprising at least one markable position. The reelabletape and the markable position are each so positioned and oriented withrespect to the spatial positioning receiver such that when the spatialpositioning receiver is moved from a first location to a secondlocation, and upon unreeling the reelable tape and using the markableposition, a detector in the spatial positioning receiver is a knowndistance from the first location of the detector in the spatialpositioning receiver prior to unreeling the reelable tape. Additionally,the markable position can comprise a detent operative upon the reelabletape.

[0034] Alternatively, the field deployable length standard can comprisea reelable tape reeled upon a reel assembly in mechanical communicationwith a housing. This reel assembly can optionally be under a spring biaswith respect to the housing so as to allow movement of the reel assemblywith respect to the housing. The spring bias can optionally allow for adesired force loading along the reelable tape. The housing can alsocomprise an aperture so shaped, sized, positioned, and oriented so as toallow a viewing of the movement of the reel assembly, with the viewingoperative to allow a calibration of the force loading along the reelabletape. Alternatively, the aperture can comprise a lens so shaped, sized,positioned and oriented so as to allow viewing of the movement of thereel assembly, with the viewing through the lens operative to allow asimilar calibration of the force loading along said reelable tape.

[0035] Another embodiment can comprise a field-deployable lengthstandard for use with a spatial positioning receiver for spatialposition-marking, setting, calibrating or referencing in a spatialpositioning system, with the field-deployable length standard comprisinga reelable tape in mechanical communication with the spatial positioningreceiver. The reelable tape comprises a first markable position, and asecond markable position a known path length along the reelable tapefrom the first markable position when the reelable tape is unreeled. Thefirst and second markable positions can be so positioned and orientedwith respect to the spatial positioning receiver when the reelable tapeis unreeled such that when the spatial positioning receiver is posed toa first location upon unreeling the reelable tape and using the firstmarkable position, a detector in the spatial positioning receiver is aknown distance with respect to the detector when the spatial positioningreceiver is posed to a second location upon unreeling the reelable tapeand using the second markable position of the reelable tape. In turn,any of the first and second markable positions can comprise a detentoperative upon the reelable tape. Optionally, the reelable tape for thisembodiment can be reeled upon a reel assembly in mechanicalcommunication with a housing.

[0036] Additionally, the reel assembly can be under an optional springbias with respect to the housing so as to allow movement of the reelassembly with respect to the housing. Optionally, this spring bias canallow for a desired force loading along the reelable tape. And, asbefore, the housing can comprise an aperture so shaped, sized,positioned, and oriented so as to allow a viewing of the movement of thereel assembly, with the viewing operative to allow a calibration of theforce loading along the reelable tape. Again, the aperture canoptionally comprise a lens so shaped, sized, positioned and oriented soas to allow the viewing of the movement of the reel assembly, with theviewing again operative to allow a calibration of the force loadingalong the reelable tape.

[0037] Further embodiments include a transmitter for a spatialpositioning system, with the transmitter having a stationary portion anda rotating laser head in proximity to the stationary portion, thestationary portion and the rotating laser head each individuallypositioned, shaped, and oriented such that there is defined an interfacevolume therebetween. The transmitter further comprises a labyrinth seal,so sized, positioned and oriented so as to restrict the motion ofcontaminants through the interface volume between the rotating laserhead and the stationary portion of the transmitter. The labyrinth sealcan optionally be so formed that a necessary path for any contaminantsis serpentine, or, in the alternative, substantially straight.Optionally, the stationary portion and the rotating laser head can eachbe individually positioned, shaped, and oriented such that the labyrinthseal is formed by at least a portion of either or both of the stationaryportion and the rotating laser head, with the labyrinth seal operativein the interface volume. Alternatively, the stationary portion and therotating laser head can comprise a rotary transformer positionedproximate the interface volume where the rotary transformer ispositioned, shaped, and oriented such that the labyrinth seal is formedby at least a portion of the rotary transformer, with the labyrinth sealagain operative in the interface volume.

[0038] Also disclosed is a method for dynamic leveling of a rotatingbody to bring a rotational axis of the rotating body into betteralignment with a desired axis. This is useful for maintainingfunctionality and accuracy of the rotating elements used in the systemsdescribed. The method comprises:

[0039] [a] Aligning an operating axis of an autocollimator to thedesired axis, with the autocollimator designed to output a light rayalong the operating axis, and the desired axis as a result of thealigning, and to monitor any reflected light rays from the light raywith respect to the desired axis;

[0040] [b] affixing a mirror to the rotating body;

[0041] [c] orienting the rotating body to within the field of view ofthe autocollimator;

[0042] [d] noting the position of the reflected light rays monitored bythe autocollimator, whereby a circular arc is formed by the reflectedlight rays;

[0043] [e] determining the direction and magnitude of a deviation of ageometric center of the circular arc from the operating axis of theautocollimator;

[0044] [f] changing the orientation of the rotating body in such amanner so as to bring the rotational axis into better alignment with theoperating axis of the autocollimator, whereby the rotational axis willbe put into better alignment with the desired axis.

[0045] If desired, the desired axis can be a downward gravitationalvector. As contemplated here, one can certainly make the rotating bodybe a rotating laser head in a spatial positioning system. Optionally,too, the mirror can be affixed to the rotating laser head in such amanner that a normal axis of the mirror is substantially parallel withthe desired axis. Alternatively, the mirror can be affixed to therotating laser head in such a manner that a normal axis of the mirror iswithin 90 degrees of the desired axis.

[0046] There is also disclosed a method for forming a spatialpositioning transmitter synchronization strobe beam to improve energydistribution and operating range when communicating with a spatialpositioning receiver operating in a field of measurement, the methodcomprising:

[0047] [a] arraying a first strobe having an output distribution of afirst value for half power beam angular width onto the field ofmeasurement;

[0048] [b] arraying a second strobe having an output distribution of asecond value for half power beam width higher than the first value forhalf power beam angular width, onto the field of measurement;

[0049] [c] the first and second strobes further positioned and orientedsuch that the operating range of the spatial positioning receiver isincreased with respect to the first and second strobes both havingeither the first value or the second value for half power beam angularwidth.

[0050] Optionally, the first value for half power angular beam width canbe less than 15 degrees, and/or the second value for half power angularbeam width can be more than 20 degrees. Also, a plurality of firststrobes can be arrayed about a single second strobe, for output of thebeam onto the field of measurement. Such a plurality can also benumerically three, as opposed to two or four. In another embodiment, theplurality of first strobes and a plurality of second strobes can beoptionally arrayed in such a manner and orientation that each strobe ofsuch first and second strobes is aimed at a distinct direction onto thefield of measurement.

[0051] In the same vein, one can also optionally select a strobe set toprovide a spatial positioning transmitter synchronization strobe beam toimprove energy distribution and operating range when communicating witha spatial positioning receiver operating in a field of measurement, withthe strobe set comprising a first strobe having an output distributionof a first value for half power beam angular width, oriented to provideoutput onto the field of measurement; a second strobe having an outputdistribution of a second value for half power beam width higher than thefirst value for half power beam angular width, oriented to provideoutput onto the field of measurement; with the first and second strobesfurther positioned and oriented such that the operating range of thespatial positioning receiver is increased with respect to the first andsecond strobes both having either the first value or the second valuefor half power beam angular width, which achieves one of many objectivessought in the instant teachings. Using this prescription, the firstvalue for half power angular beam width can again be less than 15degrees, and the second value for half power angular beam width can alsobe more than 20 degrees. Another embodiment allows that a plurality offirst strobes are arrayed about a single second strobe, for output ofthe beam onto the field of measurement; optionally the plurality can benumerically three. Optionally, the plurality of first strobes and aplurality of second strobes are arrayed in such a manner and orientationthat each strobe of such first and second strobes is aimed at a distinctdirection onto the field of measurement.

[0052] Another embodiment of the instant teachings yields a transmitterand spatial positioning receiver for a spatial positioning system, withthe system capable of switching from a horizontal mode to a verticalmode. That system comprises a stationary portion and a rotating laserhead in proximity to the stationary portion, with the rotating laserhead further comprising a first light emitting device emitting adivergent rotating light fan onto a field of measurement; asynchronization strobe providing a synchronization strobe beam forcommunicating with the spatial positioning receiver operating in thefield of measurement; a detector in the spatial positioning receiver todetect the divergent rotating light fan and also the synchronizationstrobe beam; and a processor to determine at least one spatialcoordinate of the detector in the spatial positioning receiver based ona time of receipt of the divergent rotating light fan and thesynchronization strobe beam. The transmitter and spatial positioningreceiver also comprise a sensor to sense when the transmitter isoriented so as to sweep the divergent rotating light fan in asubstantially vertical plane, the sensor communicating thisdirectionality or sense to the processor for a vertical coordinatedetermination.

[0053] Another embodiment includes various elements, such as afield-deployable spatial positioning transmitter and receiver forspatial position-marking, setting, calibrating or referencing, where thefield-deployable spatial positioning transmitter and receiver comprise atransmitter kit comprising a rotating laser head emitting an angled fanof light, where angled can mean that the fan is neither orthogonal norparallel to the plane through which the head rotates, and a strobeemitter that emits a light pulse in predetermined or programmed relationto the position of the laser head; a processor in data communicationwith a receiver; with the receiver adapted to be moved about a field ofmeasurement and determine, in conjunction with the processor, distanceand orientation. The receiver comprises a light detector, and thereceiver determines distance and orientation to the transmitter based onthe timing of detections of light from the fan of light and from thestrobe.

[0054] The receiver can optionally further comprise a field-deployablelength standard. Such a standard can comprise a reelable tape that inturn comprises at least one markable position and a reel attached to orincorporated within a housing for the receiver, the reelable tape andthe markable position each so positioned and oriented with respect tothe receiver such that when the receiver is posed at a first locationand then, upon unreeling the reelable tape and using the markableposition, a second location, the processor makes its calculations usinglight detections at the first location and second location, and a knowndistance provided by the reelable tape. The processor can optionally beattached to or incorporated within the receiver housing.Alternatively,-the rotating laser head and strobe emitter can beincorporated into or attached to a common transmitter housing.

[0055] General embodiments include a transmitter for a spatialpositioning system comprising a transmitter having a portion adapted tobe stationary during operation and a rotating laser head mounted on thestationary portion; and a labyrinth seal between the rotating laser headand the stationary portion effective to restrict the motion ofcontaminants between the rotating laser head and the stationary portion.

[0056] Another embodiment includes method for forming a spatialpositioning transmitter synchronization strobe beam to improve energydistribution and operating range when communicating with a spatialpositioning receiver operating in a field of measurement, the methodcomprising:

[0057] operating a rotating a laser head emitting an angled fan of light

[0058] periodically operating, in connection with defined rotations ofthe laser head, a first strobe having an output distribution of a firstvalue for half power beam angular width onto the field of measurement;and

[0059] periodically operating, in connection with defined rotations ofthe laser head, a second strobe having an output distribution of asecond value for half power beam width higher than the first value forhalf power beam angular width, onto the field of measurement.

[0060] In kit form, another possible embodiment includes a spatialpositioning system, with the system capable of switching between ahorizontal and a vertical mode. This system comprises a transmitter kitand a receiver kit. The transmitter kit comprises a rotating laser heademitting an angled fan of light; a transmitter processor; a strobeemitter that emits a light pulse in predetermined or programmed relationto the position of the laser head; and a sensor to sense when a housingcontaining the rotating laser head is oriented so as to sweep in asubstantially, vertical plane and communicate this information to thetransmitter processor. The receiver kit comprises a receiver processorin data communication with a receiver. The receiver processor canoptionally be the same as the transmitter processor. The receiver isadapted to be moved about a field of operation and determine, inconjunction with the receiver processor, distance and orientation. Thereceiver comprises a light detector and is adapted such that thereceiver determining distance and orientation to the transmitter arebased on the timing of detections of light from the fan of light andfrom the strobe. The transmitter processor signals the receiverprocessor of the orientation or modulates the transmitter kit lightemissions or rotation in a manner detectable by the receiver kit.

BRIEF DESCRIPTION OF THE DRAWINGS

[0061]FIG. 1 shows a cross sectional schematic view of a transmitteraccording to an embodiment of the invention.

[0062]FIG. 2 shows a top view of a receiver according to an embodimentof the invention where the top housing and battery pack are removed toillustrate internal layout of certain components of the receiver.

[0063]FIG. 3 shows a schematic block diagram for the receiver accordingto an embodiment of the invention.

[0064]FIG. 4 shows a schematic block diagram for the transmitteraccording to an embodiment of the invention.

[0065]FIG. 5 shows an oblique exploded view of a stadia mount assemblywhich is part of a field-deployable length standard for the receiveraccording to an embodiment of the invention.

[0066]FIG. 6 shows an oblique exploded view of a spring assembly whichis part of a field-deployable length standard for the receiver accordingto an embodiment of the invention.

[0067]FIG. 7 shows a cross-sectional exploded view of a portion of thetransmitter of FIG. 1, showing use of a labyrinth seal at the interfacebetween a stationary portion and a rotating laser head portion of thetransmitter according to an embodiment of the present invention.

[0068]FIG. 8 shows a closer cross-sectional view of FIG. 7, showing useof a labyrinth seal.

[0069]FIG. 9 shows the left side portion of the cross-sectional view ofFIG. 8, showing use of a labyrinth seal and a rotary transformer.

[0070]FIG. 10 shows a close view of the left side portion of thecross-sectional view of FIG. 9, according to an embodiment of theinvention having non-serpentine labyrinth seals.

[0071]FIG. 11 shows an end-on surface view of the labyrinth seal shownin FIG. 7, in a plane perpendicular to a spindle shaft of thetransmitter.

[0072]FIG. 12 shows leveling of the operating axis of an autocollimator.

[0073]FIG. 13 shows a transmitter calibration technique for the presentinvention using a mirror affixed to a rotating laser head.

[0074]FIG. 14 shows a reticle inside the autocollimator of FIG. 12,illustrating the calibration technique of the present invention.

[0075]FIG. 15 shows a transmitter calibration technique similar to thatshown in FIG. 13, but for a transmitter in a vertical mode.

[0076]FIG. 16 shows a prior art configuration of strobe light emittingdevices for azimuth synchronization.

[0077]FIG. 17 shows a longer range prior art configuration of strobelight emitting devices for azimuth synchronization.

[0078]FIG. 18 shows a configuration of strobe light emitting devices forazimuth synchronization according to the present invention.

[0079]FIG. 19 shows a unfolded 360 degree view of the strobe lightemitting devices arrayed about a transmitter according to an embodimentof the present invention.

[0080]FIG. 20 shows the detector end of a receiver according to thepresent invention.

[0081]FIG. 21 shows the detector end of a receiver according to thepresent invention, when used with a transmitter in a vertical mode.

[0082]FIG. 22 shows two transmitters positioned in a work area, where aportion of the detection volume of each transmitter overlaps defining afield of measurement.

DEFINITIONS

[0083] The following definitions shall be employed throughout:

[0084] Autocollimator shall include any optical instrument or techniquethat provides equivalent information to that given by a conventionalautocollimator as known in the field of metrology, such as where adevice uses a single lens to collimate diverging light from a slit, andthen focuses the light on a exit slit after it has passed through aprism to a mirror and been reflected back through the prism. For thisdefinition, any other device or thing, such as the interior of a 55gallon drum, could be used as a projection surface for a light rayemitted by a plumbed device, such as an autocollimator. The termautocollimator automatically includes any and all such supplementarydevices.

[0085] Azimuthal angle or azimuth shall be consistent with itsdefinition in the field of surveying and shall refer to what is knownmathematically as the polar angle theta in spherical polar coordinates(r, theta, phi). The azimuthal angle shall be the angle formed in thehorizontal plane between the horizontal projection (or component of) aspatial vector to a spatial position, and an azimuthal reference vector.Corresponding rotations representing changes in the azimuthal angleshall occur through rotations about a vertical axis. (See elevationangle).

[0086] Circular arc(s) shall include complete circles as well as subsetsegments or arcs of any angular extent.

[0087] Contaminant shall include any material, material body, particle,gas, fluid, or compound deemed undesirable and for which restriction ofmovement is sought to prevent deleterious effect(s) on selectedcomponents.

[0088] Coordinate(s) shall not be limited to whatever spatial coordinatesystem(s) is/are used herein (e.g., spherical polar (r, theta, phi)),and shall be equivalent to and convertible to other coordinate systems,such as circular cylindrical (r, theta, z), rectangular Cartesian (x, y,z), elliptic cylindrical, parabolic cylindrical, bipolar, prolatespheroidal, oblate sphereoidal, parabolic, toroidal, bispherical orother accepted coordinate systems, with or without added scaling factorsor metrics used to tailor output information to a user's needs, e.g.,aerodynamic studies over specific air foils, etc.

[0089] Detector shall include any device or devices that receive spatialposition-specific information from a transmitter, whether from a lightemitting device inside a rotating laser head, or a synchronization(strobe) pulse.

[0090] Elevation angle or elevation shall be consistent with itsdefinition in the field of surveying and shall refer to what is knownmathematically as the azimuthal angle phi in spherical polar coordinates(r, theta, phi), and not to be confused with the azimuthal angle fromthe field of surveying in the definition above. The elevation angleshall be the angle formed in the vertical plane between thevertical,projection (or component of) a spatial vector to a spatialposition, and a zero degree elevation reference vector determined bygravity. Corresponding rotations representing changes in the elevationangle shall occur through rotations about a horizontal axis. (Seeazimuthal angle).

[0091] Fan shall include divergent light or laser beams such as thosedescribed in U.S. Pat. Nos. 4,874,238 and 5,100,229.

[0092] Half power beam angular width (HPBW) shall be used here,including in the appended claims, as a mere illustration of one of manyways to characterize energy distribution as a function of solid angle(or other spatial parameters) from a strobe or light emitting device,and shall not be taken to be limiting as to other characterizations anddistribution functions that can be used.

[0093] Labyrinth seal(s) shall include non-contact seals that serve torestrict motion of fluids and/or contaminants such as particulates bythe use of surfaces in close proximity; such non-contact seals shallinclude-but not be restricted to-conventional labyrinth seals wheremotion through an interface volume takes a serpentine, curved, orlabyrinthine path.

[0094] Laser shall include any active device that uses charged speciesto convert input energy into a narrow intense beam of phase-coherentlight using stimulated emission, such as conventional laser diodes andVCSEL's (vertical cavity surface emitting lasers), and shall also bebroadened in meaning to also include any light emittingdevice-regardless of any physical, chemical, or electronic lightgenerating mechanisms used therein (such as conventional light emittingdiodes or LED's)-that possesses the requisite coherence, divergence,isotropic uniformity, electromagnetic frequency distribution andcapability of modulation to serve the purposes of this invention.

[0095] Light shall include electromagnetic radiation of any frequency,such as radio waves; microwave emissions; infrared, visible, andultraviolet light; and modulated soft and hard x-rays, and gammaemission, such as might be used for space applications where a lightemitting device that does not require input power may be required.

[0096] Light emitting device shall include a strobe as defined below,and any other device that emits electromagnetic waves of any frequencyin any manner. This shall include, for example, photoflash units, laseremitting diodes and lamps, with or without mechanical or other means,such as shutters or switchable optical filters, for modulating a timeprofile of emission.

[0097] Markable position shall refer to any means by which a location ona tape can be used to position a detector for position marking orsetting, or spatial data accumulation, including the use of physicaldetents, indexing, alignment marks or tabs, bosses, holes, hubs, or theuse of magnetic or other distinguishing materials on or about the tapesurface.

[0098] Necessary path shall denote the path that a contaminant must takein traversing a route, path or interface volume.

[0099] Pose shall refer to spatial translations, rotations, orientationsand manipulations (e.g., unfolding or unreeling) to affect a desiredresult.

[0100] Positioning shall include position measurement in a field ofmeasurement; data acquisition of position information, including mapgeneration, establishing lines, curves, and planes; setting points; anddetermining or tracking the position of any moveable object, whether byexplicit determination of position as a function of time or otherparameter, or by providing simple increments or differentials to providea similar result.

[0101] Processor shall include not only all processors, such as CPU's(Central Processing Units), but also any intelligent device thatperforms the functions given, such as analog electrical circuits thatperform the same functions. In the appended claims, the word processorcan include any processor in the receiver and/or any processor in thetransmitter.

[0102] Receiver shall include any device that receives and processesspatial position-specific information from a transmitter.

[0103] Reelable shall include the term foldable, and shall also includeany other qualities of a material body (e.g., tape) that allow it toserve as a field-deployable length standard capable of being stowed ormade more compact for storage, carrying, or additional deployment. Theterms unreeling and unreeled shall be interpreted in a similarly broadmanner.

[0104] Rotating laser head shall not require the use of a laser, andshall refer to any rotating body or rotor that serves to pan, scan,disseminate, array, divide, disperse, scatter, broadcast or distributethe output radiation of any light emitting device used for the purposesof this invention.

[0105] Serpentine shall include any labyrinthine or curved path thatinvolves angular deviation or turning along that path, including anecessary path, where the path length is longer than a straight path.

[0106] Spring bias shall include any biasing mechanism, whethermechanical, electrical, electromechanical, or of any other type, whichprovides a force as a function of deviation from an equilibriumposition.

[0107] Strobe shall include any and all light emitting devices that areused as a synchronization method serving the purposes of this invention,such as establishing datum lines or vectors, facilitatetransmitter-receiver communications, or interfacing with peripheraldevices used in conjunction with this invention.

[0108] Tape shall include strings, cables, wires, polymer extrusions,strands, threads, ropes, filaments or any medium or material body thatis capable of being posed linearly or in any other manner (e.g.,arcuate) to serve the spatial position-marking, setting, calibrating orreferencing purposes of this invention.

[0109] Transmitter shall include any device that broadcasts spatialposition-specific information to a receiver.

DETAILED DESCRIPTION OF THE INVENTION

[0110] Referring to FIG. 1 a cross sectional schematic view of atransmitter 10 according to the invention is shown. Transmitter base 12is bolted to an upper housing 14 which together enclose and support manyactive components, including a rotating laser head 16 as shown. Insiderotating laser head 16 there are installed one or more laser diodes 18or any other light emitting devices for generating a fanned laser beam20 as shown and discussed above. To condition the output of laserdiode(s) 18, a number of elements are used in a known manner, includingpassing the resultant light through a collimation lens 22, rod lens 24,and passage through a hermetically sealed exit window 26 as shown.

[0111] The entire rotating laser head 16 is supported and rotated at aconstant known angular speed via spindle shaft 28. Spindle shaft 28 isdriven in a precise manner by a known encoder motor 30, which residesinside spindle assembly 32, and is bearingly supported inside thespindle assembly 32 using shaft bearings 34. Set inside spindle assembly32 is at least one, but preferably a plurality (for better distributionand reliability) of strobes 36 used for azimuth synchronization asdiscussed herein. As shown, the spindle assembly 32 further includes astrobe window 38. Transmitter base 12 includes a battery set 40 and aplumb-down laser assembly 42 and associated exit window 44 which areused in a known manner to set the transmitter 10 at a known spot orlocation on the site or field of measurement. Transmitter base 12 alsoincludes a handle 46, keypad 48, and control electronics 50.

[0112] The spindle assembly 32 assembly as a whole is moveable onbase-mounted. gimbal pivots 52, with only one such gimbal pivot 52shown, so as to provide two tiltable degrees of freedom for levelingpurposes. As is known in the art, each such gimbal pivot 52 also hasprovision for tilting the spindle assembly 32 using a gimbal motorassembly 54, with only one such motor shown. Feedback is provided in aknown manner by three single axis level sensors 56 (one shown), whichserve to report to the control electronics 50 the angular position ortilt of the spindle assembly 32 and associated rotating laser head 16.Such single axis level sensors 56 can be fabricated using knownelectrolytic vials which are themselves calibrated independently priorto manufacture.

[0113] Encoder motor 30 has a known rotary encoder, such as a disc withholes and an optical monitor device (not shown) to generate pulses sothe control electronics 50 can regulate the motor speed, and in turn,regulate the azimuthal angular rotation rate of the fanned laser beam(s)20 that are relied upon to generate positioning information.

[0114] At the point where the rotating laser head 16 and the spindleassembly 32 are almost touching, there is provided a rotary transformer58, which provides power to the rotating laser head 16 in a known mannerusing common inductively methods, such as used in a four-head consumerVCR. Just outboard of the rotary transformer 58 as shown is a labyrinthseal 60, which will be discussed in detail below.

[0115] Now referring to FIG. 2, a cross sectional schematic view of areceiver 70 according to the invention is shown. As envisioned in thediscussion above, the receiver 70 shown comprises a detector 72, whichincorporates a known photosensitive device, such as an eight-sideddevice that has eight photocells wired in parallel so that receipt of alaser fan beam or strobe emission by the transmitter 10 of FIG. 1 can berecorded over a wide possible range of entry angles from the field ofmeasurement. Detector 72 can comprises separate detectors tailored foroptimal reception of laser fan beam(s) and strobe emissions. Forexample, a detector 72 designed for optimal detection of a strobeemission could have a larger collection aperture to allow better signalto noise ratios, especially since the strobe emission falls as inversesquare of the distance, while the laser fan beam(s) fall of as theinverse of the distance, as is known in the art. The receiver 70 asshown also includes an LCD (liquid crystal display) module 74, a circuitboard 76 for receiver electronics, and one or more connectors 78 forknown use with a detector wand, including such a wand comprising twodetectors a known distance apart, akin to the “stadia” measurementmentioned above. The receiver 70 can also comprise a user keypad 80, andthe housing 82 of the receiver 70 as shown can also accommodate abattery set 84 and include mounting provisions (not shown) for thefield-deployable length standard discussed in the figures below.

[0116] Now referring to FIG. 3, a schematic block diagram 100 ofpossible controls for the receiver 70 according to the invention isshown. Many possible schemes can be used to control the receiver 70, butgenerally, as known in the art, and discussed in the above-referencedU.S. patents, the signal path can start as shown with a DETECTORASSEMBLY 102 where the light pulses are encoded or converted toelectrical or electro-optic pulses which are conditioned by theAMPLIFIER ELECTRONICS 104 for use by TIMING ELECTRONICS 106 whichinterpret the temporal spacing of the pulses as alluded to above.CALCULATION ELECTRONICS 108 then use this information to generatecoordinates as needed. User interfacing with this information isachieved via a DISPLAY AND KEYPAD 110 as shown. Processors, includingmicroprocessors with on board memory, cache, and BIOS (basicinput/output system) can accomplish this function according to softwareexecutable instructions as known in the art.

[0117] Now referring to FIG. 4, a schematic block diagram 120 ofpossible controls for the transmitter 10 according to the invention isshown. TRANSMITTER CONTROL ELECTRONICS 122 as shown providefunctionality to perform transmitter functions, including a MOTOR DRIVEinput 124 to the ROTOR MOTOR 126 which drives the rotating laser headwhich in turn, via the ROTARY ENCODER 130 gives SPEED FEEDBACK 132 tothe TRANSMITTER CONTROL ELECTRONICS 122. TRANSMITTER CONTROL ELECTRONICS122, comprising one or more processors, provides selective energizing ofone or light emitting devices, shown here as STROBE ASSEMBLY 134.TRANSMITTER CONTROL ELECTRONICS 122 also function to provide a GIMBALMOTOR DRIVE 136 to the GIMBAL MOTORS 138 as shown, which in turnmechanically influence the GIMBAL ASSEMBLY 140, causing three LEVELSENSORS 142 to alter their LEVEL FEEDBACK 144 in a known manner asshown. This information is used in a known feedback loop to control thetilt or leveling of the rotating laser head.

[0118] The scale reference mentioned above is provided for by use of afield-deployable length standard, such as a “setup cable” or similarmaterial body which will be discussed here. The setup cable is aretractable cable that is integrated into a stadia pole receiver mountor similar assembly. In one embodiment, the user to attaches the end ofthe cable to a fixed object, pulls the cable out several inches to afirst detent, applies tension, and takes a measurement. Then the userreleases the cable lock and backs up with the receiver 70 until thecable reaches a second detent, which is exactly 10 m from the first.

[0119] Referring now to FIGS. 5 and 6, oblique exploded views of apossible stadia mount assembly 150 and spring assembly 152,respectively, which are part of a field-deployable length standard forthe receiver according to the invention are shown. These two figuresshow variants of what is envisioned as part of the invention. Thefield-deployable length standard can be mounted directly on, or madeintegral with, the receiver as previously described. Referring initiallyto FIG. 6, inside the field-deployable length standard, a reelable tapeor spring tape 154 is reeled upon a center hub 156, both residing in aninside reel, shown as portions or views inside reel left 158 and insidereel right 160. The inside reel 158, 160 is in turn housed inside aninner reel 162, 164, which acts as a housing for the reelable tape orspring tape 154, and keeps the spring tape 154 reeled and deployable.The spring tape 154 comprises a markable position 166 that provides away of setting a position of the receiver. As shown, the mark 166 isimplemented as a detent, but any other mechanism or technique can beused consistent with the definition above for markable position.

[0120] Referring to FIG. 5, the inside reel floats under bias usingspring 168 which is affixed to the inside reel as described. Inpractice, one deploys the reelable tape or spring tape 154 by posing orextending spring tape 154, which can be affixed to a known feature inthe field of measurement, and taking a position reading using thereceiver, while the tape is unreeled and the inside reel is positionedupon a markable position. A receiver position reading (not shown) takenat an original position of the spring tape 154 with respect to theinside reel can provide, with the position obtain from the markableposition, a distance standard as envisioned. To keep the tension orforce loading of the reelable tape constant from measurement tomeasurement, the position of the inside reel can be monitored using anaperture in a reel housing 170, 172, with or without use of a lens 174as shown to allow better alignment of the inside reel with respect tothe reel housing. The use of a detent as the markable position on thespring tape 154 can be facilitated by the use of a button 176 and buttonholder 178, as shown, which allow a spring pin 180 to engage or cause toengage that detent. In this way, a reproducible field-deployable lengthstandard is provided that is compact and allows a fair degree ofmeasurement reproducibility. Another embodiment is provided when thespring tape 154 comprises two markable positions, in which case thefield-deployable length standard can be posed twice, with receiverposition readings taken for each pose, thus providing a length standardas envisioned here.

[0121] Now referring to FIG. 7, a portion of the cross-sectional view ofFIG. 1, showing use of a labyrinth seal is shown. One embodiment of thisinvention provides for use of a labyrinth seal 60 as shown, at or nearthe interface between the rotating laser head 16 and the spindleassembly 32, in lieu of felt, rubber, or other rotary seals which havethe disadvantages as cited above. The transmitter 10 shown can alsocomprise a rotary transformer 58 as discussed above, and shown in thefigure inboard of the labyrinth seal 60. Contaminants 62 are in theambient environment around the transmitter 10, and entry of contaminants62 in the general direction shown by the arrow 63 can potentially resultin contamination of spindle shaft 28 and other critical components,resulting in opening up of tolerances and poor performance. Thelabyrinth seal 60 incorporates a serpentine path 64 along a necessarypath that the contaminants 62 must take to enter critical areas. Such alabyrinth seal 60 can be a separate component pressed or installed intothe rotating laser head 16 and spindle assembly 32, or can be formedtherefrom by machining or other known processes.

[0122] Referring now to FIG. 8, a closer cross-sectional view of FIG. 7is shown. An interface volume 66 as shown provides a narrow, serpentinenecessary path for contaminants 62 and thereby slows entry into spindleshaft 28 and related areas. The serpentine nature of the necessary pathbreaks up laminar flow of contaminants 62 and provide sinks foraccumulated contaminants that would otherwise have an opportunity toenter in an undesirable manner. Referring now to FIG. 9, the left sideportion of the cross-sectional view of FIG. 8 is shown, showing use of alabyrinth seal 60 and a rotary transformer 58 having separate inductiveportions 58A and 58B as shown.

[0123]FIG. 10 shows a close view of the left side portion of thecross-sectional view of FIG. 9, but with non-serpentine labyrinth sealsto illustrate two things: the rotary transformer 58 can itself bemodified, machined, or formed to operate as a labyrinth seal 60, and thelabyrinth seal 60 interface volume can be straight, that is,non-serpentine. Specifically, the labyrinth seal 60 can have anon-serpentine interface volume 68 and the rotary transformer 58 canhave a non-serpentine interface volume 69, which individually(separately) or both (if both are made to be labyrinth seals) can serveto provide a discouraging necessary path for contaminants 62.

[0124]FIG. 11 shows an end-on surface view of the labyrinth seal 60shown in FIG. 7, in a plane perpendicular to spindle shaft. Theconcentric rings 61 as shown are indicative of the serpentine nature ofthe necessary path for contaminants 62 as they start to migrate acrossthis figure toward the center 65 as shown.

[0125] Referring now to FIG. 12, a conventional leveling of theoperating axis of an autocollimator 202, a known process by which anautocollimator 202 secured by an autocollimator foot 204 is leveled orplumbed to have its operating axis 206 as shown to be in alignment withthe gravitational vector. The output of the autocollimator is set upon amercury pool 208 and the autocollimator 202 is adjusted in position(notably, its operating axis 206) until the operating axis 206 of theautocollimator 202 becomes a desired axis 210, which in this case isdetermined by gravity. This is done in a known manner by adjustingautocollimator 202 and its operating axis 206 until the place where thereflected beam from mercury pool 208 hits a reticle 212 or functionallysimilar component or surface in the same projected location as theoriginating beam.

[0126] Now referring to FIG. 13, a transmitter calibration technique 220is given for the present invention using a mirror 222 affixed to therotating laser head 224 as shown. It does not matter whether the mirror222 is flat on its underside, or whether it is not level with respectthe rotating laser head 224. The mirror 222, once affixed to therotating laser head 224, defines a rotor axis 226, which may or may notreflect well the rotation axis (not shown) of the rotating laser head224. However, this generally will not affect the final result.

[0127] Presumably, the rotating laser head 224 needs calibration; andits rotation axis is not true or along a desired axis 226 as shown. Forexample, after the transmitter 10 levels itself, there may still bedeviation about gimbal axis 228 and the rotating laser head, 224 may betilted with respect to the desired axis 226, with the positioning of thetransmitter housing and components 230 taken into account. One placesmirror 222 on the rotating laser head 224, and shines the light outputof autocollimator 202 upon the mirror 222 with the rotating laser head224 rotating in the normal manner. The resultant reflected light willgive valuable and easily obtainable, information.

[0128]FIG. 14 shows a reticle 212 inside the autocollimator 202 of FIG.12, illustrating the calibration technique of the present invention. Theresultant reflected light forms a circle, circular arc or arc 232, whichmay be divined using the cross hairs 234 or the equivalent in theautocollimator 202, whose reticle 212 may have gradations or rulings.236 as shown. In this method, the magnitude and direction of thedeviation of the center 238 of the arc 232 indicates precisely themisalignment of the rotor spin axis 226 (as shown in FIG. 13), and thetransmitter can be appropriately calibrated to bring the center 238 ofthe arc 232 into alignment with the operating axis 210 of theautocollimator 202. The diameter of the arc 232 indicates the amount ofwobble and this information can be discarded, as it is not relevant tothe calibration of the rotating laser head spin axis with the desiredaxis.

[0129]FIG. 15 shows a transmitter calibration technique 250 similar tothat shown in FIG. 13, but for a transmitter in vertical mode, where theoperating axis 206 of the autocollimator 202 is set to a desired axisthat is other than gravitational, e.g., horizontal. For this purpose theautocollimator 202 may be aligned using the known technique given, butthis time using a pentaprism 252 or other device in conjunction withmercury pool 208, as is known.

[0130]FIG. 16 shows a prior art configuration 300 of strobe lightemitting devices for azimuth synchronization, where a transmitter on atripod 302 is set a ground plane 304 in a field of measurement andstrobes are used to periodically light up the field using IREDs(infra-red emitting diodes) or other light emitting devices. The strobedevices shown here to illustrate have a half power beam angular width(HPBW) that is shown nominally at 25 degrees, resulting in a widedivergence 306 and a wide radiant intensity distribution 308. Such adistribution can be obtain using IRED devices under the tradenameOPTEK290, for example. Radiant intensity distribution 308 results in arange (RANGE1) which is not long range enough from the transmitter, andresults in wasted energy 310 which typically spills onto the groundsurface.

[0131] In FIG. 17, a longer range prior art configuration 320 of strobelight emitting devices for azimuth synchronization is shown, with anarrow divergence 322 (using, for example, OPTEK295 IREDs), resulting ina narrow radiant intensity distribution 324, giving a long range RANGE2,but resulting in wasted energy 326, which actually is a lack of energy,and results in no appreciable strobe signal in the 326 area, limitingthe fiduciary volume over which the spatial positioning system canfunction.

[0132] A solution is shown in FIG. 18, where a configuration 340 ofstrobe light emitting devices for azimuth synchronization according tothe present invention is shown. One seeds the array of strobes withlight emitting device of both narrow and wide divergencecharacteristics, namely, at least one wide divergence strobe providing awide radiant intensity distribution, and at least one narrow divergencestrobe providing a narrow radiant intensity distribution. The result, asshown, gives a mixed divergence characteristic 342, a long range RANGE3,and good coverage near the transmitter and minimal wasted energy 344. Ofcourse, it is envisioned that many strobes can be used, and FIG. 19shows a unfolded 360 degree view of the strobe light emitting devicesarrayed about a transmitter according to the present invention.

[0133] Referring to FIG. 19, a strobe set 402 is shown, with theunfolded 360 degree view “flattened” into a strip S-STRIP forillustration purposes. In practice, the strobes are only arrayed aboutan angular field of 270 degrees, but this shall not be limiting in thisdisclosure. As shown, strobes having a narrow divergence distribution404, shown with “X's” are placed throughout the array. Seeded amongthese devices, perhaps one for every three 404 strobes, are widedistribution strobes 406, as envisioned above and in the appendedclaims.

[0134]FIG. 20 shows the detector end of a receiver 500 according to thepresent invention, with a detector 502, photodiodes 504 arrayed insidethe detector 502, covered by an infra-red transmissive cover 506. Thedetector 502 rides on a photocell base 510 which is articulatable by apivot shaft 512. The pivot shaft may be part of the photocell base 510.The receiver 500 further includes a position sensing switch and detent514, which indicates to the receiver electronics that the detector 502has been flipped up as shown. The photocell base 510 can include amarking point as well known in the art. As shown, the transmitter 500 ishoused in a receiver housing 518.

[0135] Now referring to FIG. 21, the detector end of a receiver 500according to the present invention, when used with a transmitter in avertical mode, is shown. In this mode, the receiver 500 is posed suchthat the detector 502 “views” the field of measurement horizontally, inanticipation of detecting laser fans that are rotating in a verticalplane, as is known. Photocell base 510 is flipped down into the receiverhousing 518 for this purpose. Instead of prior art transmitters, where atransmitter must be dedicated to vertical scanning, the invention allowsthat the transmitter electronics and/or the receiver electronics are“informed” of a vertical positioning of the transmitter by knownposition sensors in the unit, and the spatial positioning system is usedin conjunction with the receiver 500 thus described.

[0136] The fan sweep frequency for the vertical and horizontal modes canbe different to allow differentiation by processors and calculationengines. Appropriate vertical vials can be provided and sensed at theappropriate time. By communicating the vertical mode (by virtue ofposition sensing, and not by elaborate setup methods or by dedication ofunits) directly to processors, automatic vertical mode position sensingin the field of measurement, even for tall buildings, can be obtained.

[0137] The setup cable described above obviates need for a “scale bar”to determine locations and give a scale to measurements alreadyaccumulated. In the case where there is no two-detector measurement wandor pole (stadia-type measurements), there is a need for quick fielddeployable means for easily setting scale. One can take numerous(redundant) measurements, which can then be averaged by processingalgorithms. A “carpenter's” folding level is a possible embodiment forthe posing of the field-deployable length standard.

[0138] Typically, each laser transmitter scans light across a fieldextending 270 degrees horizontally and 60 degrees vertically. Thisscanning creates a detection or fiduciary volume over which thetransmitter output may be detected by the receiver for positionmeasurement. Referring to FIG. 22, two or more transmitters 602 can bepositioned so that their detection volumes 604 overlap defining a fieldof measurement 606. In the field of measurement 606, a receiver 608 candetermine up to three or more position variables 610, typically twospatial coordinates (e.g., azimuth, elevation) per twin beam lasertransmitter 602.

[0139] All publications and references, including but not limited topatents and patent applications, cited in this specification are hereinincorporated by reference in their entirety as if each individualpublication or reference were specifically and individually indicated tobe incorporated by reference herein as being fully set forth. Any patentapplication to which this application claims priority is alsoincorporated by reference herein in its entirety in the manner describedabove for publications and references.

What is claimed is:
 1. A spatial positioning system, comprising: atransmitter having: a rotating laser head adapted to emit light in theshape of a divergent rotating fan onto a field of measurement, asynchronization strobe adapted to provide a synchronization strobe beamin said field of measurement, said synchronization strobe includingfirst strobes having first divergence characteristics, wherein saidstrobe beam has overall divergence characteristics different from saidfirst divergence characteristics of said first strobes; and a sensoradapted to sense when said transmitter is oriented to sweep saiddivergent rotating light fan about a desired axis and communicate suchorientation for a spatial coordinate determination; a receiverpositionable in said field of measurement having a detector to detectsaid divergent rotating light fan and said synchronization strobe beam;and a processor adapted to determine at least one spatial coordinate ofsaid receiver based on the detection of said divergent rotating lightfan and said synchronization strobe beam.
 2. The spatial positioningsystem according to claim 1, wherein said processor is furtherconfigured to determine said at least one spatial coordinate uponreceipt from said transmitter of an indication that said transmitter isoriented to sweep said divergent rotating light fan about said desiredaxis.
 3. The spatial positioning system of claim 1, in which saidtransmitter changes the sweep frequency of said transmitter when saidsensor senses that said transmitter is oriented to sweep said divergentrotating light fan is rotated about said desired axis.
 4. The spatialpositioning system according to claim 1, wherein said desired axis issubstantially vertical.
 5. The spatial positioning system according toclaim 1, wherein said desired axis is substantially vertical.
 6. Thespatial positioning system according to claim 1, wherein said desiredaxis is adjustable between a vertical and a horizontal orientation. 7.The spatial positioning system according to claim 1, wherein saidoverall divergence characteristics includes both narrow and widedivergence characteristics.
 8. The spatial positioning system accordingto claim 1, wherein said synchronization strobe further comprises secondstrobes having a second divergence characteristics, wherein said strobebeam has overall divergence characteristics different from said firstdivergence characteristics of said first strobes and said seconddivergence characteristics of said second strobes.
 9. The spatialpositioning system according to claim 8, wherein: said first strobescomprise narrow divergence characteristics; said second strobes comprisewide divergence characteristics; and said overall divergencecharacteristics comprises a mixture of narrow and wide divergencecharacteristics.
 10. The spatial positioning system of claim 1, in whichsaid receiver includes a photodetector that may be pivoted with respectto said receiver so as to facilitate operation.
 11. A spatialpositioning system, comprising: a transmitter having: a rotating laserhead adapted to emit light in the shape of a divergent rotating fan ontoa field of measurement, a synchronization strobe adapted to provide asynchronization strobe beam in said field of measurement, saidsynchronization strobe beam having a first radiant intensitydistribution; and a sensor adapted to sense when said transmitter isoriented to sweep said divergent rotating light fan about a desired axisand communicate such orientation for a spatial coordinate determination;a receiver positionable in said field of measurement having a detectorto detect said divergent rotating light fan and said synchronizationstrobe beam; and a processor adapted to determine at least one spatialcoordinate of said detector in said receiver based on the detection ofsaid divergent rotating light fan and said synchronization strobe beam.12. The spatial positioning system according to claim 11, wherein saidsynchronization strobe further provides a strobe beam having a secondradiant intensity distribution, wherein said strobe beam has an overallradiant intensity distribution different from said first and secondradiant intensity distributions.
 13. A spatial positioning systemcapable of operating in a horizontal or a vertical mode, comprising: atransmitter adapted to produce and rotate an angled fan of lightselectively about either a substantially horizontal or a substantiallyvertical axis, said transmitter including: a transmitter processor; astrobe emitter that emits a light pulse in predeterminerelation to theposition of the angled fan of light; and a sensor adapted to sense andcommunicate to said transmitter processor when said angled fan of lightis sweeping about a substantially vertical axis; a receiver, including alight detector adapted to be positioned in a field of operation anddetect said strobe and said angled fan of light; and a receiverprocessor in data communication with said receiver, said receiverprocessor operatively configured to determine an azimuth and anelevationof said receiver with respect to said transmitter based ontiming of detections of said fan of light and from said light pulse fromsaid strobe emitter; and further in which said transmitter processorsignals said receiver processor that said angled fan of light issweeping about a desired axis.
 14. A transmitter and spatial positioningreceiver for a spatial positioning system, said system capable ofswitching between a horizontal and a vertical mode, said systemcomprising: a spatial positioning receiver for positioning within afield of measurement, including a detector for detecting light atransmitter emitting a divergent rotating light fan onto said field ofmeasurement and having a synchronization strobe providing asynchronization strobe beam onto said field of measurement, saidtransmitter pivotable between said horizontal and vertical modes andfurther including a first sensor to sense when said transmitter isoriented so as to sweep said divergent rotating light fan about asubstantially vertical axis and a second sensor to sense when saidtransmitter is oriented so as to sweep said divergent rotating light fanin a substantially horizontal axis; and a processor to determine atleast one spatial coordinate of said detector based on a time of receiptof at least one of said divergent rotating light fan and saidsynchronization strobe beam.
 15. A laser transmitter, comprising: arotating laser head adapted to emit light in the shape of a divergentrotating fan onto a field of measurement, a synchronization strobeadapted to provide a synchronization strobe beam in said field ofmeasurement, said synchronization strobe including first strobes havinga first divergence characteristic, wherein said strobe beam has overalldivergence characteristics different from said first divergencecharacteristics from said first strobes; and a sensor adapted to sensewhen said transmitter is oriented to sweep said divergent rotating lightfan about a desired axis and communicate such orientation for a spatialcoordinate determination.
 16. A laser transmitter capable of switchingbetween a horizontal and a vertical mode, said system comprising: adivergent rotating light fan directed onto a field of measurement; asynchronization strobe providing a synchronization strobe beam onto saidfield of measurement; a first sensor to sense when said transmitter isoriented so as to sweep said divergent rotating light fan about asubstantially vertical axis; and a second sensor to sense when saidtransmitter is oriented so as to sweep said divergent rotating light fanin a substantially horizontal axis.
 17. A spatial positioning systemcomprising: at least two transmitters, each transmitter having: arotating laser head adapted to emit light in the shape of a divergentrotating fan defining a detection volume; a synchronization strobeadapted to provide a synchronization strobe beam, said synchronizationstrobe including first strobes having a first divergence characteristic,wherein said strobe beam has overall divergence characteristicsdifferent from said first divergence characteristics of said firststrobes; and a sensor adapted to sense when said transmitter is orientedto sweep said divergent rotating light fan about a desired axis andcommunicate such orientation for a spatial coordinate determination;wherein each of said at least two transmitters are positioned so thatsaid detection volume of each transmitter at least partially overlapsdefining a field of measurement; a receiver positionable in said fieldof measurement having a detector to detect said divergent rotating lightfan and said synchronization strobe beam from each transmitter; and aprocessor adapted to determine at least one spatial coordinate of saiddetector in said receiver based on the detection of said divergentrotating light fan and said synchronization strobe beam from at leastone transmitter.
 18. The spatial positioning system according to claim17, wherein said processor determines at least one of azimuth andelevation from a select one of said at least two transmitters.
 19. Thespatial positioning system according to claim 17, wherein more than twoposition variables are determined based upon the detection of saiddivergent rotating light fan and said synchronization strobe beam fromat least two transmitters.
 20. The spatial positioning system accordingto claim 17, wherein two spatial coordinates are determined from eachtransmitter.
 21. The spatial positioning system according to claim 20,wherein said two spatial coordinates comprise azimuth and elevation. 22.A spatial positioning system comprising: at least two transmitters, eachtransmitter configured to scan light across a field extendinghorizontally and vertically, defining a detection volume over which saiddivergent rotating fan can be detected by a receiver, wherein saidtransmitters are positionable such that at least a portion of saiddetection volume of each transmitter overlaps defining a field ofmeasurement wherein at least one position variable may be determined bysaid receiver; each transmitter further comprising: a synchronizationstrobe adapted to provide a synchronization strobe beam in said field ofmeasurement, said synchronization strobe including first strobes havinga first divergence characteristics, wherein said strobe beam has overalldivergence characteristics different from said first divergencecharacteristics of said first strobes.
 23. The spatial positioningsystem according to claim 22, wherein said receiver is programmed tocompute up to three position variables within said field of measurement.24. A spatial positioning system comprising: at least two transmitters,each transmitter configured to scan light across a field extendinghorizontally and vertically, defining a detection volume over which saiddivergent rotating fan can be detected by a receiver, wherein saidtransmitters are positionable such that at least a portion of saiddetection volume of each transmitter overlaps defining a field ofmeasurement wherein at least one position variable may be determined bysaid receiver; each transmitter further comprising: a synchronizationstrobe adapted to provide a synchronization strobe beam in said field ofmeasurement, said synchronization strobe including first strobes havinga first radiant intensity distribution, wherein said strobe beam has anoverall radiant intensity distribution different from said first radiantenergy distribution.
 25. The spatial positioning system according toclaim 2, wherein said receiver is programmed to compute up to threeposition variables within said field of measurement.